1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.eclipse.aether.internal.impl;
20
21 import java.io.ByteArrayOutputStream;
22 import java.io.File;
23 import java.io.IOException;
24 import java.io.UncheckedIOException;
25 import java.nio.ByteBuffer;
26 import java.nio.channels.Channels;
27 import java.nio.channels.FileChannel;
28 import java.nio.channels.FileLock;
29 import java.nio.channels.OverlappingFileLockException;
30 import java.nio.file.Files;
31 import java.nio.file.NoSuchFileException;
32 import java.nio.file.Path;
33 import java.nio.file.StandardOpenOption;
34 import java.util.Map;
35 import java.util.Properties;
36
37 import org.slf4j.Logger;
38 import org.slf4j.LoggerFactory;
39
40 /**
41 * Manages access to a properties file in legacy compatible way.
42 * <p>
43 * Note: the file locking in this component (that predates {@link org.eclipse.aether.SyncContext}) is present only
44 * to back off two parallel implementations that coexist in Maven (this class and {@code maven-compat} one), as in
45 * certain cases the two implementations may collide on properties files. This locking must remain in place for as long
46 * as {@code maven-compat} code exists.
47 * <p>
48 * This implementation should be used when multiple, legacy Maven versions (older than 3.10.x) share same local repository
49 * concurrently.
50 *
51 * @since 2.0.17
52 * @see NamedLocksTrackingFileManager
53 * @see TrackingFileManagerSupplier
54 */
55 public final class LegacyTrackingFileManager implements TrackingFileManager {
56 private static final Logger LOGGER = LoggerFactory.getLogger(LegacyTrackingFileManager.class);
57
58 @Deprecated
59 @Override
60 public Properties read(File file) {
61 return read(file.toPath());
62 }
63
64 @Override
65 public Properties read(Path path) {
66 // existence, not readability: an unreadable tracking file must fail, not read as "untracked"
67 if (Files.exists(path)) {
68 synchronized (mutex(path)) {
69 try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.READ);
70 FileLock unused = fileLock(fileChannel, true)) {
71 Properties props = new Properties();
72 props.load(Channels.newInputStream(fileChannel));
73 return props;
74 } catch (NoSuchFileException e) {
75 LOGGER.debug("No such file to read {}: {}", path, e.getMessage());
76 } catch (IOException e) {
77 LOGGER.warn("Failed to read tracking file '{}'", path, e);
78 throw new UncheckedIOException(e);
79 }
80 }
81 }
82 return null;
83 }
84
85 @Deprecated
86 @Override
87 public Properties update(File file, Map<String, String> updates) {
88 return update(file.toPath(), updates);
89 }
90
91 @Override
92 public Properties update(Path path, Map<String, String> updates) {
93 try {
94 Files.createDirectories(path.getParent());
95 } catch (IOException e) {
96 LOGGER.warn("Failed to create tracking file parent '{}'", path, e);
97 throw new UncheckedIOException(e);
98 }
99 synchronized (mutex(path)) {
100 try (FileChannel fileChannel = FileChannel.open(
101 path, StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.CREATE);
102 FileLock unused = fileLock(fileChannel, false)) {
103 Properties props = new Properties();
104 if (fileChannel.size() > 0) {
105 props.load(Channels.newInputStream(fileChannel));
106 }
107
108 for (Map.Entry<String, String> update : updates.entrySet()) {
109 if (update.getValue() == null) {
110 props.remove(update.getKey());
111 } else {
112 props.setProperty(update.getKey(), update.getValue());
113 }
114 }
115
116 LOGGER.debug("Writing tracking file '{}'", path);
117 ByteArrayOutputStream stream = new ByteArrayOutputStream(1024 * 2);
118 props.store(
119 stream,
120 "NOTE: This is a Maven Resolver internal implementation file"
121 + ", its format can be changed without prior notice.");
122 fileChannel.position(0);
123 int written = fileChannel.write(ByteBuffer.wrap(stream.toByteArray()));
124 fileChannel.truncate(written);
125 return props;
126 } catch (IOException e) {
127 LOGGER.warn("Failed to write tracking file '{}'", path, e);
128 throw new UncheckedIOException(e);
129 }
130 }
131 }
132
133 @Deprecated
134 @Override
135 public boolean delete(File file) {
136 return delete(file.toPath());
137 }
138
139 @Override
140 public boolean delete(Path path) {
141 if (Files.isReadable(path)) {
142 synchronized (mutex(path)) {
143 try (FileChannel fileChannel = FileChannel.open(path, StandardOpenOption.WRITE);
144 FileLock unused = fileLock(fileChannel, false)) {
145 Files.delete(path);
146 return true;
147 } catch (NoSuchFileException e) {
148 LOGGER.debug("No such file to delete {}: {}", path, e.getMessage());
149 } catch (IOException e) {
150 LOGGER.warn("Failed to delete tracking file '{}'", path, e);
151 throw new UncheckedIOException(e);
152 }
153 }
154 }
155 return false;
156 }
157
158 /**
159 * This method creates a "mutex" object to synchronize on thread level, within same JVM, to prevent multiple
160 * threads from trying to lock the same file at the same time. Threads concurrently working on different files
161 * are okay, as after syncing on mutex, they operate with FS locking, that goal is to synchronize with possible
162 * other Maven processes, and not with other threads in this JVM.
163 */
164 private static Object mutex(Path path) {
165 // The interned string of path is (mis)used as mutex, to exclude different threads going for same file,
166 // as JVM file locking happens on JVM not on Thread level. This is how original code did it ¯\_(ツ)_/¯
167 return canonicalPath(path).toString().intern();
168 }
169
170 /**
171 * Tries the best it can to figure out actual file the workload is about, while resolving cases like symlinked
172 * local repository etc.
173 */
174 private static Path canonicalPath(Path path) {
175 try {
176 return path.toRealPath();
177 } catch (IOException e) {
178 return canonicalPath(path.getParent()).resolve(path.getFileName());
179 }
180 }
181
182 private FileLock fileLock(FileChannel channel, boolean shared) throws IOException {
183 FileLock lock = null;
184 for (int attempts = 8; attempts >= 0; attempts--) {
185 try {
186 lock = channel.lock(0, Long.MAX_VALUE, shared);
187 break;
188 } catch (OverlappingFileLockException | IOException e) {
189 // For Unix process sun.nio.ch.UnixFileDispatcherImpl.lock0() is a native method that can throw
190 // IOException with message "Resource deadlock avoided"
191 // the system call level is involving fcntl() or flock()
192 // If the kernel detects that granting the lock would result in a deadlock
193 // (where two processes are waiting for each other to release locks which can happen when two processes
194 // are trying to lock the same file),
195 // it returns an EDEADLK error, which Java throws as an IOException.
196 // Read another comment from
197 // https://github.com/bdeployteam/bdeploy/blob/7c04e7228d6d48b8990e6703a8d476e21024c639/bhive/src/main/java/io/bdeploy/bhive/objects/LockableDatabase.java#L57
198 // Note (cstamas): seems this MAY also happen where there is ONE process but performs locking on same
199 // file from multiple threads, as Linux kernel performs lock detection on process level.
200 if (attempts <= 0) {
201 throw (e instanceof IOException) ? (IOException) e : new IOException(e);
202 }
203 try {
204 Thread.sleep(50L);
205 } catch (InterruptedException e1) {
206 Thread.currentThread().interrupt();
207 }
208 }
209 }
210 if (lock == null) {
211 throw new IOException("Could not lock file");
212 }
213 return lock;
214 }
215 }